JP2000272981A - Hardened cement body and method for producing the same - Google Patents

Abstract

(57) [Problem] To provide a high-strength hardened cement body and a method for producing the hardened cement body in a short time. SOLUTION: This molded article is formed by kneading cement, aggregate and water, and is subjected to a carbonation treatment under heating and pressure in an initial stage of a cement hydration reaction, and preferably has a porosity of 0. 2 or less cement hardened body, and a method for producing a cement hardened body, wherein a molded body formed by kneading cement, aggregate and water is subjected to a carbonation treatment under heating and pressure at an initial stage of a cement hydration reaction, In the initial stage of the cement hydration reaction, a molded body formed by kneading cement, aggregate, and water is subjected to a carbonation treatment under a heated and pressurized state after, for example, once performing preliminary curing by a carbonation treatment or the like. Manufacturing method of hardened cement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-strength hardened cement body and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a method of increasing the strength of a hardened cement body by carbonation treatment, calcium hydroxide generated by hydrating cement by exposing the hardened cement body to carbon dioxide gas is converted into calcium carbonate. There is known a method of filling the pores of a cured product to increase the strength.
However, in this conventional method, it is difficult to carbonate the inside of the hardened cement body, and there is a problem that the effect of the carbonation treatment is not sufficiently exhibited.

Therefore, Japanese Patent Application Laid-Open No. Hei 6-263562 proposes a method in which after the hydration reaction of cement starts to be activated, curing is performed in a carbon dioxide gas atmosphere to further promote carbonation and densification. .

However, even in the method proposed above, the strength of the obtained cured product needs to be further improved, and it takes a long time to cure in a carbon dioxide gas atmosphere, and it is necessary to improve the productivity. There was a problem.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems in the conventional method for producing a hardened cement body, and provides a high-strength hardened cement body and a hardened cement body in a short time. It is intended to provide a method of manufacturing.

[0006]

In order to achieve the above-mentioned object, the present invention according to claim 1 is a molded article formed by kneading cement, aggregate and water, wherein the molded article is formed by a cement hydration reaction. Provided is a cement hardened body characterized in that it is subjected to a carbonation treatment under heating and pressure in an initial stage. The present invention according to claim 2 is characterized in that a molded body formed by kneading cement, aggregate and water is subjected to carbonation under heating and pressure at an initial stage of a cement hydration reaction.
The present invention also provides a method for producing the hardened cement body described above.

According to a third aspect of the present invention, a molded product obtained by kneading cement, aggregate and water is subjected to a pre-curing process in an initial stage of a cement hydration reaction, and then to a heating and pressurizing process. 2. A method for producing a hardened cement according to claim 1, wherein carbonation treatment is performed. Claim 4
The present invention as described above provides a method for producing a hardened cement according to claim 3, wherein the method of pre-curing is a carbonation treatment.

According to the present invention, a molded product obtained by kneading a Portland cement, an aggregate and water is prepared by mixing a calcium silicate compound contained in the cement with a hydration rate of 3%.
In the initial stage of the cement hydration reaction in the range of 0% or less, the carbonation treatment condition is such that the water content of the molded body during the carbonation treatment is 0.075 to 0.5 by weight of water / cement, Pressure is 50-200kg / cm2, temperature is 80-200
The method for producing a hardened cement body according to claim 1, wherein the carbonation treatment is performed at a temperature of 10C for 10 to 60 minutes. The present invention according to claim 6 provides the hardened cement according to claim 1, wherein the porosity after the carbonation treatment is 0.2 or less. Hereinafter, the present invention will be described in more detail.

The cement used in the present invention is not particularly limited as long as calcium hydroxide is produced upon hydration. For example, ordinary portland cement, special portland cement, alumina cement and the like can be used. Portland cement is preferred in that the effect of densification during carbonation is large.

[0010] Portland cement is a cement mainly composed of an unhydrated calcium silicate compound generally called alite (C3S: 3CaO.SiO2) or belite (C2S: 2CaO.SiO2). Portland Cement, Early Portland Cement, Ultra Early Portland Cement, Medium Heat Portland Cement, Low Heat Portland Cement, Sulfate Resistant Portland Cement,
Examples include portland cements such as various low alkali type portland cements, mixed cements such as blast furnace cements, silica cements, fly ash cements, and white cements.

Examples of the aggregate used in the present invention include aggregates for cement mortar such as silica sand and river sand, inorganic fillers such as calcium carbonate and diatomaceous earth, wood chips, pulp, and various fibers.

The cement and the aggregate are mixed at a predetermined ratio, then a required amount of water is added, and the mixture is kneaded by a conventionally known device, and is conventionally kneaded, for example, a compression molding method.
It is formed into a predetermined shape by an extrusion molding method or the like. Among them,
The extrusion molding method is preferably employed from the viewpoint of productivity, and the compression molding method is preferably employed from the viewpoint of finally obtaining a high-strength hardened cement body.

The cured cement according to the first aspect of the present invention is a cured cement obtained by subjecting a molded article obtained from a cement, an aggregate and water to, for example, a compression molding method, an extrusion molding method, or the like as described above, and performing a carbonation treatment. And can be obtained, for example, by the production method according to the present invention.

The hardened cement according to the present invention according to the sixth aspect is the hardened cement according to the first aspect, wherein the porosity after the carbonation treatment is 0.2 or less. Here, the porosity of the hardened cement body refers to the ratio of voids contained in the hardened cement body measured by a known method such as an underwater immersion method or a mercury intrusion method. When the porosity of the hardened cement according to the present invention is 0.2 or less, the strength improving effect is remarkably higher than when the porosity after the carbonation treatment exceeds 0.2.

In the method for producing a hardened cement according to the present invention, the initial stage of the cement hydration reaction means that immediately after the cement and water are mixed, the hardened body undergoes a setting phenomenon. Refers to a period immediately before the intensity is developed. This period is, for example, when cured at 20 ° C., within about 24 hours immediately after the cement and water are mixed. When the carbonation treatment is performed at the stage where hydration or hardening has progressed, a hydrated structure is formed to some extent, and the effect of improving strength by filling between the structures can be obtained, but a dramatic improvement in strength as in the present invention is achieved. No effect.

[0016] The carbonation treatment in the present invention refers to a treatment in which an alkali component, particularly a calcium component, is carbonated in the hardening process of cement. As the carbonation treatment, for example, a method of treating with carbon dioxide can be mentioned. Specifically, a method of using gas, carbon dioxide in a supercritical state under heating and pressure in the initial stage of the cement hydration reaction Is mentioned.

In the method for producing a hardened cement according to the third and fourth aspects of the present invention, the pre-curing means that the molded body can be released from the mold before the full-scale carbonation treatment is performed. This is a curing treatment for the purpose of curing to a degree. The pre-curing treatment is not particularly limited as long as the molded body can be cured in a short time immediately after the start of molding to such an extent that the molded body can be maintained, and for example, steam curing or carbonation treatment can be used. In particular, as set forth in claim 4,
The carbonation treatment is preferable because it can be cured to a target cured state in a short time.

As described in claim 5, when Portland cement is used as the cement, the degree of progress of the cement hydration reaction can be indicated by the hydration rate of the calcium silicate compound contained in the cement. The initial stage of the hydration reaction means that the hydration rate is 30% or less, more preferably 20% or less. Although the lower limit of the hydration rate is not particularly limited, if the water necessary for the carbonation reaction is supplied during the carbonation treatment, the hydration rate becomes 0% (unhydrated, substantially immediately after molding). Carbonation treatment may be performed from a very close state.

In the present invention, the hydration ratio of the calcium silicate compound is defined as A: the amount of the unhydrated calcium silicate compound contained in the cement raw material, and B: the amount of the remaining unhydrated calcium silicate compound when the hydration ratio is measured. Then, ｛(AB) / A｝ × 10
Refers to the value indicated by 0. As a method for measuring the amount of the unhydrated calcium silicate compound (alite and belite) in the cement, a known method using an X-ray diffraction measuring device or each magnetic resonance device (silicon, 29Si NMR) can be used ( References for NMR-based methods: G. Parry-Jo
nes, Cement and Concrete Research, Vol. 19, p228-23
4, 1989,).

In the case of producing a hardened product by carbonating a Portland cement containing an unhydrated calcium silicate compound, the hydration of the unhydrated calcium silicate compound greatly contributes to the development of strength. Even if the advanced sample is carbonated, a dramatic improvement in strength cannot be obtained.

In the present invention, the water content of the molded article at the time of carbonation treatment, expressed by the weight ratio of water / cement, refers to the weight of water contained in the molded article immediately before the carbonation treatment, It is the value divided by the weight. The weight ratio of the water / cement is preferably in the range of 0.075 to 0.5. If this value is smaller than 0.075, the reaction with carbon dioxide does not sufficiently occur, and the efficiency of the carbonation reaction decreases. Conversely, if the value is larger than 0.5, excess water existing between cement particles diffuses carbon dioxide. This is because the carbonation reaction in the initial stage of the hydration reaction does not sufficiently occur.

When the weight ratio of water / cement of the formed green body before the carbonation treatment is lower than 0.075, water is newly added, and conversely, when the weight ratio is higher than 0.5. Excess water is removed by suction or the like.
The range may be 0.5. The optimum water / cement ratio depends on the amount of cement and aggregate added. However, when Portland cement is used as the cement of the present invention, the water / cement ratio is most preferably 0.1 to 0.4. preferable.

The heating temperature is preferably 50 ° C. or higher, more preferably in the range of 80 ° C. to 200 ° C. If the heating temperature is lower than 50 ° C, it takes a long time to sufficiently cause the carbonation reaction.On the other hand, if the heating temperature is higher than 200 ° C, the carbonation reaction becomes faster but requires a lot of energy. At the same time, when additives such as aggregate used include organic reinforcing fibers, there is a risk that the fibers and the like are liable to undergo thermal deterioration.

The above pressure is 5 kg / c.
m2 or more, more preferably 50 to 20
It is within the range of 0 kg / cm2. If the pressure is lower than 5 kg / cm2, the permeability of carbon dioxide into the molded product and the amount of carbonation reaction decrease, and the carbonation reaction does not occur sufficiently or it takes a long time for the carbonation reaction to fully occur. Cost. on the other hand,
Even if the pressurizing pressure is higher than 200 kg / cm2, the progress of the carbonation reaction does not greatly change, and on the contrary, a large amount of energy is required, which is not suitable from the viewpoint of industrial productivity and enlargement of equipment.

The time of the carbonation treatment depends on the type and mixing ratio of the cement and the aggregate to be used, but is preferably within 24 hours when the treatment is performed within the above-mentioned preferable temperature and pressure ranges. , More preferably within the range of 10 to 60 minutes. If the treatment time is shorter than 10 minutes, the carbonation reaction does not sufficiently occur. On the other hand, if the processing time is longer than 24 hours, no further effect can be obtained. Conversely, it is not industrially reasonable in terms of energy consumption and equipment. In the case of producing the hardened cement body having the highest strength in the production method of the present invention, the object can be achieved by producing the cured body in various more preferable ranges including the above-mentioned carbonation treatment conditions. Specifically, the water / cement ratio when obtaining the molded body before the carbonation treatment is set to 0.1 to 0.5, and the carbonation treatment condition is set to a temperature of 80 to
200 ° C., pressure 50-200 kg / cm 2 and time 10
This can be achieved by setting the range to 60 minutes. Also,
If a certain strength is required, the above 80 to 20
The object can be achieved by performing the treatment at a temperature lower than 0 ° C. × 50 to 200 kg / cm 2 × time of 10 to 60 minutes, at a low pressure or for a long time.

The conditions of the carbonation treatment used for the pre-curing vary depending on the composition of the excipient to be used and the like. However, in consideration of the rapidity of the treatment and the scale of the production equipment, the subsequent conditions of the cement hydration reaction are considered. It is preferable that the treatment is performed at a lower pressure as compared with the main curing treatment in which carbonation is performed under heating and pressure in the initial stage.

From the same point, the processing temperature is preferably high and short, specifically, the pressure is 1 to 150 kg / cm.
2. The temperature is preferably room temperature or higher, more preferably 40 ° C. or higher, and the time is preferably 1 hour or less. This is because an excessive pressure necessitates an increase in the size of the device. Further, if the temperature is low, the carbonation reaction requires time, and if more than one hour is required for preliminary curing, there is no point in separating the steps into preliminary curing and main curing.

(Function) The hardened cement according to the present invention comprises:
Since the compact is subjected to carbonation under heating and pressure at the initial stage of the cement hydration reaction, the structure becomes more dense due to carbonation compared to the structure of the cement hardened body formed only by the cement hydration reaction alone. For example, even if the porosity is the same, high strength is exhibited. Furthermore, the cement hardened body having a porosity of 0.2 or less, which is lower than the conventional one, exhibits extremely high strength as compared with the conventional cement hardened body, in combination with the carbonation treatment in the initial stage of the hydration reaction. -ing

In the method for producing a hardened cement according to the present invention, a molded body obtained by kneading cement, aggregate and water is subjected to carbonation under heating and pressure at an initial stage of a cement hydration reaction. In the carbonation treatment in the long-term curing step of the conventional method, the hydration reaction of the cement and the carbonation start to proceed simultaneously, whereas the carbonation reaction in the initial stage of the hydration reaction of the cement is performed in the method of the present invention. Progresses in a short time.

That is, in the early stage of the hydration reaction of cement, before the formation of various calcium silicate hydrates (CSH gels) which usually contribute to the strength of the hardened cement, the carbonation treatment is carried out. Since calcium carbonate is generated and the hardened component of the cement forms a dense structure in a short time, a product having a remarkably high strength can be obtained as compared with the hardened cement obtained by the conventional method.

In addition, according to the method for producing a hardened cement according to the present invention, the time required for developing the strength is reduced as compared with the conventional method, and the hardened cement can be manufactured with high productivity. Further, in the above method, immediately after the start of molding of the molded article, once the pre-curing is performed, and then the carbonation treatment is performed under heating and pressure, the pre-curing facilitates handling in the manufacturing process, It is possible to efficiently release from the mold and fill the autoclave for full curing with high efficiency.

Further, when the pre-curing is performed by a carbonation treatment, the pre-curing is performed in a short time, so that the effect of improving the strength by the carbonation reaction of the main curing is not hindered, and the productivity is further improved. Can be enhanced. When Portland cement is used as the cement, the volume expansion of the unhydrated calcium silicate compound during carbonation increases the strength by carrying out the carbonation treatment at the stage containing a large amount of unhydrated calcium silicate compound. This greatly contributes to obtaining a product having a remarkably high strength as compared with the hardened cement obtained by the conventional method.

[0033]

(Examples 1 to 3) 100 parts by weight of ordinary Portland cement, 50 parts by weight of No. 8 silica sand, 1 part by weight of hydroxypropylmethylcellulose (2% by weight aqueous solution at 20 ° C. having a viscosity of 30,000 cps), polypropylene fiber (Length 6 mm) 5 parts by weight were added and mixed. To this mixture was added 40 parts by weight of water, further mixed, and kneaded with a kneader.
It was compression-molded at cm 2 to obtain a flat molded body having a thickness of 5 mm.

The obtained molded body was aged at 20 ° C. for the time shown in Table 1. Thereafter, the molded body was placed in an autoclave and subjected to carbon dioxide treatment under the conditions (temperature, pressure, treatment time) shown in Table 1 to obtain a hardened cement body having increased strength.

Example 4 Using the same raw materials as in Example 1, a molded product was obtained through the same steps. The hydration rate of the obtained molded product was 3%, and this was immediately applied to a pressure of 1 kg / cm 2.
After being placed in an atmosphere of carbon dioxide at 50 ° C. for 40 minutes, the mold was released from the mold and subjected to carbon dioxide treatment under the same conditions as in Example 1 to obtain a hardened cement body having increased strength.

[Measurement of Flexural Strength of Hardened Cement Body] The hardened cement body obtained in each of Examples and Comparative Examples was cut into a predetermined size to obtain a test piece, and the bending strength was measured in accordance with JIS A1408. The results are shown in Table 1.

[Measurement of Hydration Ratio] In each of Examples and Comparative Examples, the hydration ratio of the calcium silicate compound immediately before the carbon dioxide treatment was measured by 29 Si NMR, and the values are shown in Table 1. The measuring method was as follows. 29SiNMR was measured using JNL-LA500 manufactured by JOEL, and the measurement was performed by the MASGHD method under the condition of 5000 times of integration. After the measurement, a sharp peak around -70 ppm derived from the unhydrated calcium silicate compound (-57 to -75 ppm) and a relatively broad peak around -82 ppm derived from the hydrated calcium silicate gel (-75 to -8
(8 ppm) was measured, and the respective numerical values were calculated as α and β to calculate {β / (α + β) × 100, which was taken as the hydration rate of the calcium silicate compound.

[Measurement of porosity] A part of the produced hardened cement was cut out, and the dry weight (W1), the weight of the saturated sample in water (W2), and the surface dry weight of the saturated sample (W3) were measured. It was determined by the following equation. P = 1− (W 1 −W 2) / (W 3 −W 2) The dry weight (W 1) is the weight of the test piece dried at 60 ° C. for one week, and the weight of the saturated sample in water (W 2) is the dry test The piece was immersed in water and degassed in vacuum for 8 hours, then the weight measured in water and the surface dry weight of the saturated sample (W3)
Is the weight measured by wiping off the water adhering to the surface of the saturated sample.

[0039]

[Table 1]

(Comparative Example 1) A hardened cement pillar was obtained in the same manner as in Example 1, except that the curing time was changed to 30 hours. The bending strength and the like were measured, and the measured values are shown in Table 1.

Comparative Example 2 Using the same raw materials as in Example 1, a molded article was obtained through the same steps. After 15 hours from the mixing of the raw materials, the molded body was cured under a normal pressure carbon dioxide atmosphere at a room temperature of 20 ° C. for 6 days to obtain a hardened cement body. The bending strength and the like were measured, and the measured values are shown in Table 1.

Comparative Example 3 Using the same raw materials as in Example 1, a molded product was obtained through the same steps. The obtained molded body was cured by curing at room temperature of 20 ° C. for 7 days (carbonation treatment was not performed). The bending strength and the like were measured, and the measured values are shown in Table 1.

As is apparent from Table 1, in Examples 1 to 4, carbonation was carried out at an initial stage of the hydration reaction under a condition where the hydration rate of the calcium silicate compound was 30% or less and under heating and pressure. Compared to Comparative Example 3 which was cured by ordinary room temperature curing for a day and was not subjected to the carbonation treatment, it exhibited much higher flexural strength. Further, in Example 4, when the same carbonation treatment as in Example 1 was performed after the preliminary curing, the same improvement in strength was exhibited, and release from the mold immediately after the preliminary curing was also possible.

In Comparative Example 1, the hydration reaction progressed.
After 0 hour, that is, after the initial stage of the cement hydration reaction, the same carbonation treatment as in Example 1 was performed. However, the bending strength was improved as compared with Comparative Example 3 by densification by carbonation. However, since the hydration ratio of the calcium silicate compound during the carbonation treatment was 30% or more, the effect of improving the bending strength as in Examples 1 to 4 was not obtained.

Further, in Comparative Example 2, carbon dioxide was placed in an atmosphere of carbon dioxide at normal pressure, and heated and pressurized carbon dioxide was not used. Was less than that of Examples 1-4.

[0046]

The hardened cement of the present invention is constituted as described above, and is subjected to a carbonation treatment in the initial stage of the hydration reaction. It expresses extremely high strength in comparison. When the porosity of the cured product after the carbonation treatment is set to 0.2 or less, which is lower than the conventional value, higher strength can be exhibited.

The method for producing a hardened cement according to the present invention is constituted as described above. According to the method of the present invention, the carbonation reaction proceeds in a short period of time in the initial stage of the hydration reaction of cement, A product having a significantly higher strength can be obtained as compared with the cured cement obtained by the method. In addition, the time required for developing the strength is shorter than that of the conventional method, and the production method is industrially highly productive.

Further, by providing a pre-curing step in the method for producing a hardened cement body of the present invention, the mold can be released at an early stage after molding, the handling in the manufacturing process becomes easy, and efficient use of the molding die and The autoclave for the main curing can be used efficiently and can be reduced in size, and the production cost can be reduced. Furthermore, when the pre-curing is performed by carbonation treatment, the pre-curing is performed in a short time, so that the effect of improving the strength by the carbonation reaction of the main curing is not hindered, and the pre-curing can be shared with the main curing equipment. Thereby, the total manufacturing cost can be reduced.

In particular, at the initial stage of the cement hydration reaction in which the calcium silicate compound has a hydration ratio of 30% or less, the carbonation condition is determined by the portland cement as the cement. Has a water content of water /
If the weight ratio of cement is 0.075 to 0.5, the pressure is 50 to 200 kg / cm2, the temperature is 80 to 200 ° C, and the treatment time is within the range of 10 to 60 minutes, By performing the carbonation treatment, the volume expansion of the unhydrated calcium silicate compound contained in the Portland cement greatly contributes to the strength development, and the carbonation structure is formed in a short time, and the cement hardened body is further improved. This has the effect of improving strength and productivity.

 ──────────────────────────────────────────────────続 き Continued on the front page (31) Priority claim number Japanese Patent Application No. 11-9394 (32) Priority date January 18, 1999 (Jan. 18, 1999) (33) Priority claim country Japan (JP) (72) Inventor Kunio Kusano 2-2 Familiar, Sekisui Kagaku Kogyo Co., Ltd. 2-2 Kamikaba Kamichocho, Minami-ku, Kyoto 4G012 RA02 RA05 4G055 AA01 AB01 AC01 BA03

Claims (6)

[Claims] Claims: 1. A hardened cement formed by kneading cement, aggregate and water, which is formed by carbonation under heating and pressure in an initial stage of a cement hydration reaction. body. 2. The cement hardening according to claim 1, wherein the molded body formed by kneading the cement, the aggregate and the water is subjected to a carbonation treatment under heating and pressure in an initial stage of the cement hydration reaction. How to make the body. 3. A process in which a molded body formed by kneading cement, aggregate, and water is subjected to a pre-curing process in an initial stage of a cement hydration reaction, followed by a carbonation treatment under heating and pressure. The method for producing a hardened cement body according to claim 1, wherein: 4. The method for producing a hardened cement according to claim 3, wherein the pre-curing method is a carbonation treatment. 5. A molding obtained by kneading Portland cement, aggregate, and water, and forming a molded body obtained by kneading the calcium silicate compound contained in the cement at an initial stage of a hydration reaction of 30% or less. In the stage, the carbonation conditions are such that the water content of the compact during the carbonation treatment is 0.075 to 0.5 by weight of water / cement, and the pressure is 50 to 200.
kg / cm2, temperature 80-200 ° C, processing time 10-60
The method for producing a hardened cement according to claim 1, wherein the carbonation treatment is performed within a range of minutes. 6. The hardened cement according to claim 1, wherein the porosity after the carbonation treatment is 0.2 or less.